Here is a YouTube video about Four Ways to Solve Least Squares Problems, and is part of a growing collection of videos I have found to be useful. The reason is detailing the four ways to solve least-squares problems. Solving least-squares problems comes in to play in the many applications that rely on data fitting and understanding science related to software defined radio.
This tutorial, "Four Ways to Solve Least Squares Problems" is free education you can watch, which will help you deepen your knowledge and be better prepared for licence exams, schoolwork, or operating radio equipment.